Real or Imaginary? (On pair creation in de Sitter space)

TL;DR

This paper demonstrates that a properly defined Feynman propagator in de Sitter space leads to a non-zero imaginary part of the scalar field effective action, indicating particle production at the Gibbons-Hawking rate.

Contribution

It introduces a specific Feynman propagator consistent with the composition principle, linking it to particle creation in de Sitter space.

Findings

Non-zero imaginary part of the effective action in even-dimensional de Sitter space.

Particle production rate matches the Gibbons-Hawking rate.

Propagator obeys the composition principle from prior work.

Abstract

Using properly defined Feynman propagator we obtain non--zero imaginary contribution to the scalar field effective action in even dimensional de Sitter space. Such a propagator follows from the path integral in de Sitter space and obeys composition principle proposed in arXiv:0709.2899. The obtained expression for the effective action shows particle production with the Gibbons--Hawking rate.